As one of processing functions of Voice over Internet Protocol (VoIP) that terminates Real-time Transport Protocol (RTP) and RTP Control Protocol (RTCP), call-disconnection watchdog timer processing is provided. In the call-disconnection watchdog timer processing, RTP and RTCP transfers are monitored in talking, and if both packets cannot be received for a specified time period, a call is terminated. For example, as call termination processing, a “BYE” message is generated in Session Initiation Protocol (SIP), for example.
A network communication path, through which the same voice quality as that of a fixed-line telephone network is required, is constructed by a device, such as a router, etc., in which Resource reSerVation Protocol (RSVP) is implemented, for example. Such a network communication path employs a redundant configuration which is a network configuration reducing or preventing communication paths from going down when a failure occurs in the device.
If an abnormality occurs in an RSVP refresh message, resource bandwidth reservation of a relay router is deleted, and a gateway determines that the quality of the communication path cannot be maintained, and thus terminates a call. If an abnormality is detected by call-disconnection monitoring, the gateway terminates a call, and deletes resource bandwidth reservation of the relay router by an RSVP disconnection message.
In this case, the gateway of a call transmission source might have failed, and thus it is not possible to determine that the relay router has failed unconditionally. However, if the relay router has failed, when a new call goes through the failed relay router, a call disconnection occurs again, and reliability of communication cannot be maintained. And thus, it takes time to search for a location where the failure has occurred.
As a method of monitoring a telephone speech quality, there is a method of detecting an abnormality of the telephone speech by monitoring RTP and RTCP. In the case where RTP and RTCP are monitored only by a gateway, if an abnormality occurs at any one of relay routers constituting a network, it takes time to search for a failure, namely, to identify the occurrence location of the abnormality.
Thus, in order to detect an abnormality of a network, it is thought that an RTP/RTCP monitor is also implemented in relay routers constituting the network.
For example, Japanese Laid-open Patent Publication No. 2005-73211 has disclosed a method of notifying an abnormality detected by a relay router to a server that monitors relay routers, maintenance personnel, etc., as a quality report.